In the past, these Republican candidates have disparaged the idea of global warming. “We’re not going to make America a harder place to create jobs in order to pursue policies that will do absolutely nothing, nothing, to change our climate,” Marco Rubio said in a Republican debate in September.

Donald Trump uttered this marvel: “I am not a believer, and I will, unless somebody can prove something to me, I believe there’s weather. I believe there’s change, and I believe it goes up and it goes down, and it goes up again.”

Ted Cruz, who seems enthralled with the idea of a climate-science conspiracy, said last week, “Climate change is the perfect pseudoscientific theory for a big-government politician who wants more power.” On Saturday, Mr. Cruz had nothing to say.

Let’s hope the candidates’ new silence suggests that they see that when 195 nations together recognize the need for immediate action, their arguments to do nothing seem more misguided than ever.